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Method and apparatus for efficiently tracking queue entries relative to a timestamp

United States Patent

June 17, 2014
View the Complete Patent at the US Patent & Trademark Office
An apparatus and method for tracking coherence event signals transmitted in a multiprocessor system. The apparatus comprises a coherence logic unit, each unit having a plurality of queue structures with each queue structure associated with a respective sender of event signals transmitted in the system. A timing circuit associated with a queue structure controls enqueuing and dequeuing of received coherence event signals, and, a counter tracks a number of coherence event signals remaining enqueued in the queue structure and dequeued since receipt of a timestamp signal. A counter mechanism generates an output signal indicating that all of the coherence event signals present in the queue structure at the time of receipt of the timestamp signal have been dequeued. In one embodiment, the timestamp signal is asserted at the start of a memory synchronization operation and, the output signal indicates that all coherence events present when the timestamp signal was asserted have completed. This signal can then be used as part of the completion condition for the memory synchronization operation.
Blumrich; Matthias A. (Ridgefield, CT), Chen; Dong (Croton On Hudson, NY), Gara; Alan G. (Mount Kisco, NY), Giampapa; Mark E. (Irvington, NY), Heidelberger; Philip (Cortlandt Manor, NY), Ohmacht; Martin (Yorktown Heights, NY), Salapura; Valentina (Chappaqua, NY), Vranas; Pavlos (Danville, CA)
International Business Machines Corporation (Armonk, NY)
11/ 768,800
June 26, 2007
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OF DEVELOPMENT The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Contract. No. B554331 awarded by the Department of Energy.